BACKGROUND AND OBJECTIVES:Subependymal giant cell astrocytomas (SEGA) are low-grade intraventricular tumors generally associated with tuberous sclerosis complex. Although mechanistic target of rapamycin inhibitors are recommended as first-line therapy for progressive SEGA without hydrocephalus, surgery is still relevant because 40% of patients are drug resistant. This study aimed to evaluate surgical outcomes in terms of tumor control, complication rates, and ventriculoperitoneal shunt (VPS) requirement, through a single-center retrospective series and a meta-analysis. METHODS:We retrospectively analyzed 31 pediatric SEGA resections performed over 2 decades at a tertiary care center. Clinical, radiological, and surgical variables were examined to identify predictors of outcome. In addition, a systematic literature review and meta-analysis were conducted to contextualize our findings. RESULTS:Gross total resection was achieved in 64.5% of cases, with a 19.3% rate of transient postoperative complications and a 6.4% incidence of VPS placement. No permanent morbidity or mortality occurred. Favorable outcome was associated with a smaller tumor volume and absence of preoperative hydrocephalus. The meta-analysis confirmed that preoperative hydrocephalus was the main predictor of postoperative complications (odds ratio 2.30) and shunt dependence (odds ratio 3.45). Five-year progression-free survival was 90.9% in the gross total resection subgroup and 100% in patients with unilateral tumors. Bilateral tumor location was an independent predictor of recurrence (hazard ratio = 17.79, P = .02). CONCLUSION:Microsurgical resection of SEGA is a safe and effective therapeutic option, particularly in patients without hydrocephalus. Early surgical intervention may reduce the need for VPS and long-term complications, offering a valid alternative or complement to mechanistic target of rapamycin inhibitor therapy, with durable tumor control especially in unilateral cases.

Diffuse leptomeningeal glioneuronal tumour (DLGNT) is rare a glioneuronal neoplasm of the central nervous system, which occurs mainly in children and adolescents characterized by the presence of MAPK pathway alteration and 1p deletion. Clinical, radiological and molecular data from 20 patients diagnosed with DLGNT from May 2001 to May 2023 were collected. Clinical presentation was polymorphous, with intracranial hypertension and back pain as most common symptoms. Patients underwent multiple lines of treatment (median of 4, range 1–8) in addition to surgery with a median follow up of 94 months (range 7–241). Radiotherapy and carboplatin-based chemotherapy were the 2 treatments with the higher number of partial response (PR) and stable disease (SD) of 7/10 and 2/10 for radiotherapy and 7/12 and 5/12 for carboplatin-based chemotherapy. All patients treated with trametinib progressed before 2 years, while 2-years PFS was of 52

OBJECTIVES:Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has emerged as a minimally invasive alternative for drug-resistant epilepsy and pediatric brain tumors, particularly in deep-seated lesions where open surgery presents significant risks. However, the multimodal imaging characteristics of lesions during and after MRgLITT remain underexplored. This study aims to describe the MRI features of MRgLITT-treated lesions in pediatric patients both intraoperatively and during long-term follow-up. METHODS:We conducted a retrospective analysis of 26 pediatric patients(32 procedures) treated using MRgLITT, including focal cortical dysplasias, low-grade tumors and hamartomas. Imaging acquisition included preoperative, intraoperative, and postoperative MRI with advanced sequences(T1-weighted, FLAIR, DWI, ASL perfusion, and MR spectroscopy). Lesion evolution was assessed over a one-year follow-up period. RESULTS:Intraoperatively, lesions showed a rim of high signal on DWI and on post-contrast T1-weighted images, a lactate peak on MR spectroscopy, and the majority of them had peripheral high signal on FLAIR associated with a low signal core and increased CBF on ASL. During follow-up, lesions may increase in size in the first days or weeks, then decrease in size mainly in the first 3 months and tend to stabilize at 9 months, with persistent gliotic changes on FLAIR sequences. Contrast enhancement resolved in epilepsy-related lesions, but small areas remained in most tumors without correlation with progression. CONCLUSION:MRgLITT results in a predictable pattern of imaging changes, with lesion contraction occurring primarily within the first 3 months. Understanding these radiological markers is essential for optimizing post-procedure management and treatment decisions in pediatric epilepsies and tumors.

OBJECTIVE Craniosynostoses are an underrecognized cause of intracranial hypertension (ICH), especially when associated with congenital syndromes. Alagille syndrome (ALGS) is a multisystem disorder with typical facial features and hepatobiliary, cardiac, vascular, skeletal, and ocular manifestations. The occurrence of craniosynostosis in ALGS is rare and can be associated with chronic ICH, requiring craniofacial surgery to increase the intracranial volume. The authors report a series of 6 patients with ALGS with craniosynostosis and discuss their neurosurgical management. METHODS The authors included all patients with ALGS and craniosynostosis assessed in their national reference center between 2012 and 2024. They collected the following parameters: date of birth; sex; JAG1 mutation; hepatobiliary, cardiac, vascular, skeletal and ocular symptoms; type of craniosynostosis; presence of papilledema; head circumference; type of surgery (if needed); and clinical outcome. RESULTS The 6 patients had a median age of 6 years at referral (range 15 months-6 years). Four patients presented with a history of ICH and papilledema. Craniofacial CT scans showed the fusion of all sutures (coronal, sagittal, and lambdoid) in 2 patients; bicoronal plus bilambdoid synostosis in 1 patient; and sagittal plus bilambdoid synostosis 1 patient. All patients required biparietal floating craniotomies, leading to prompt improvement of papilledema. Two patients without a history of ICH presented with single-suture synostosis without papilledema (anterior plagiocephaly and scaphocephaly). CONCLUSIONS The authors report single-suture and multisuture craniosynostosis associated with ALGS and its association with chronic ICH. They suggest systematic screening for craniosynostosis in patients with ALGS and papilledema to avoid unrecognized chronic ICH.

Pediatric brain arteriovenous malformation (PbAVM) is a potentially life-threatening condition accounting for intracerebral hemorrhage and other neurological complications. Our study aimed to elucidate the relationships between PbAVM angioarchitecture, spatial distribution, and clinical presentation. This retrospective study included all consecutive PbAVMs managed in a tertiary pediatric center (2007–2023). We performed a hierarchical clustering based on quantitative imaging data and constructed a 3D MRI-based atlas. We derived and analyzed clusters for initial presentation, clinical parameters (cure, recurrent bleeding, proliferation/recurrence, seizures) and location. We included 245 pediatric brain arteriovenous malformations in 234 patients (74.8

We aimed to decipher the natural history of paediatric cerebral and intraspinal medullary cavernous malformations and their genetic background, with an emphasis on the effect of mutational burden on their radiological features and haemorrhagic risk. We retrospectively collected clinical and radiological data and the natural history of the disease during the follow-up of all consecutive patients with cavernous malformations over the last 2 decades at a unique paediatric centre. We created an MRI atlas after lesion segmentation and normalization to perform voxel-based lesion symptom mapping. Targeted germline DNA sequencing of CCM1-3 genes and somatic lesions and targeted sequencing of RAS and PI3 K pathway genes were performed. In total, 257 patients carrying 786 brain and 14 spinal cavernous malformations were analysed. Age at diagnosis was 9.5 ± 5 years. Follow-up data were available for 718 lesions with a mean follow-up of 5.59 ± 3.28 years. Then, 134 brain (80 with focal onset seizures) and 10 spinal cavernous malformations were surgically excised. Furthermore, 95 of the/144 DNA extracted from lesions were successfully sequenced for somatic variants (PIK3CA, MAP3K3, KRIT1 and KRAS). We found an annual haemorrhagic risk of 1.9%, which was increased by type (sporadic or postradiation), location (brainstem or spinal), and radiological parameters (extracapsular haemorrhage, volume, signal, or presence of developmental venous anomaly). Cavernous malformations symptoms and radiological features were highly dependent on brain location. Surgical risk for cortical brain lesions was 0.9%, with 85% international league against epilepsy score grade of 1-2. Furthermore, 62% of operated lesions carried a pathogenic PIK3CA variant. The MAP3K3 somatic variant alone or in association with a PIK3CA variant decreased the annual haemorrhagic risk by 4.8 ± 1.5 (P < 0.05). We confirmed that 96% of cavernous malformations that are satellites of a developmental venous anomaly carried a PIK3CA variant and increased the relative haemorrhagic risk by 3 ± 0.31 (P = 3.8.10-3). We report an annual haemorrhagic risk of 1.9%, which is modulated by radiological features (i.e. extracapsular haemorrhage, volume, signal, and location) and lesion type. Here, we describe the first MRI atlas. Surgery yields excellent general outcomes in supratentorial superficial lesions, unlike deep-seated cavernous malformations, which is associated with high morbidity. Molecular diagnosis of operated lesions highlighted PIK3CA as a factor associated with aggressiveness in both sporadic and familial cavernous malformations. MAP3K3 decreased the risk. Finally, we confirmed that developmental venous anomaly is a radiological landmark of PIK3CA.

INTRODUCTION:Laser Interstitial Thermal Therapy under MRI control has emerged as a safe and efficient alternative to microsurgery in epilepsy and neurooncology procedures. Yet it has been used only recently in seldom European centers. Here, we report our 4 years' experience with LITT in children (complications, epileptic and oncologic outcomes). METHODS:Single center retrospective study of consecutive LITT procedures during the 2021-2024 period. LITT was restricted to pediatrics in the following indications: (i) circumscribed lesion (ii) benign pathology (iii) problematic location for microsurgical resection. After a robotic stereotactic implantation, ablation was performed under MRI guidance with the VISUALASE system. Post operative outpatient clinic and MRI were systematic at 1, 3, 6 and 12 months. Epileptic outcome was defined after ILAE classification, oncological relapse was defined as a volumetric increase after 1 month of follow up. RESULTS:35 children (mean age 11.4yo, M/F ratio = 0.8) were operated in 41 successive procedures. Main indication was focal epilepsy (n = 28 patients; FCD n = 13, LEAT n = 11, HH n = 4) while 7 children were treated for oncological purposes. Lesions were cortical in the insula (n = 8), mediotemporobasal (n = 8) and paracentral (n = 6) regions or subcortical (hypothalamus and basal ganglia n = 6, mesencephalon n = 4). Perioperative transient adverse events occurred in 25.7% and persistent neurological deficit was noted in 2 children. After a mean follow up of 31.2 months, 67.9% of the patients are seizure free and tumoral recurrence was observed in 3/18 cases. CONCLUSION:In this pediatric cohort of 35 children with challenging brain lesions, LITT ablation was safe and efficient.

PURPOSE:Thalamic gliomas are found predominantly in children and can be classified into two main types with different prognoses and management: diffuse midline glioma (DMG) H3K27-altered and low-grade glioma (LGG). Our aim was to find imaging features distinguishing these tumors and to develop a diagnostic score. PATIENTS AND METHODS:A retrospective study spanning September 1999 to May 2021 involved pediatric patients with thalamic gliomas, categorized into H3K27-altered DMG and LGG groups. Preoperative imaging, including morphology, diffusion, and arterial-spin-labeling perfusion, was reviewed blindly and compared between the two groups. A diagnostic score was formulated based on significant findings. Results were validated using an internal and external validation cohort. RESULTS:Sixty-six patients were included (median age, 9 years; interquartile range [IQR] [5-13]; 38 girls) with 37 DMG H3K27-altered and 29 LGG. DMG H3K27-altered tumors exhibited larger volumes (median 64 cc, IQR [36-88] vs 26 cc, IQR [15-37], p < 0.001), greater heterogeneity in T2-weighted signal and enhancement (62% [22/37] vs 31% [9/29], p = 0.04, and 97% [32/33] vs 56% [15/27], p = 0.0008, respectively), lower minimum relative apparent diffusion coefficient (ADC) (0.92 (IQR [0.76-1.23]) vs 1.55 (IQR [1.40-1.72]), p < 0.001), and higher relative maximum cerebral blood flow (CBF) levels (2.08 (IQR [1.48-3.05]) vs 0.84 (IQR [0.45-1]), p < 0.001). A diagnostic score integrating tumor diameter, solid content predominance, relative ADC, and relative CBF achieved 100% sensitivity and specificity in distinguishing DMG H3K27-altered tumors from LGG (full score available for 36 patients), with good results in external and internal validation cohorts (12 patients). CONCLUSION:The morphological, diffusion, and arterial spin labeling imaging characteristics of pediatric thalamic tumors enable excellent differentiation of DMG H3K27-altered and LGG.

A novel histomolecular tumor of the central nervous system (CNS), the “diffuse glioneuronal tumor with oligodendroglioma-like features and nuclear clusters (DGONC),” has recently been identified, based on a distinct DNA methylation profile and has been added to the 2021 World Health Organization Classification of CNS Tumors. This glioneuronal tumor mainly affects the supratentorial area in children and recurrently presents with a monosomy of chromosome 14. Herein, we report the case of a DNA-methylation based diagnosis of DGONC having atypical features, such as pseudo-rosettes and the absence of a chromosome 14 monosomy, thus rendering its diagnosis very challenging. Because of the wide variety of morphologies harbored by DGONC, a large range of differential diagnoses may be hypothesized from benign to malignant. Interestingly, the current case, like one previously reported, exhibited a co-expression of OLIG2, synaptophysin and SOX10, without GFAP immunopositivity. This particular immunophenotype seems to be a good indicator for a DGONC diagnosis. The classification of DGONC amongst glioneuronal or embryonal tumors is still debated. The clinical (a pediatric supratentorial tumor), morphological (from a benign oligodendroglioma-like tumor with microcalcifications and possible neuropil-like islands to a malignant embryonal tumor with a possible spongioblastic pattern), and immunohistochemical (co-expression of OLIG2 and synaptophsyin) profiles resemble CNS, neuroblastoma, FOXR2-activated and may potentially bring them together in a future classification. Further comprehensive studies are needed to conclude the cellular origin of DGONC and its prognosis.

Background: The literature lacks a combined analysis of neurosurgical microvascular anastomosis training models. We performed a systematic literature search to provide an overview of the existing models and proposed a classification system based on the level of simulation and reproducibility of the microvascular anastomosis. Methods: The systematic literature search followed the PRISMA guidelines. We consulted MEDLINE, Web of Knowledge, and EMBASE independently for papers about bypass training models. Every training model was analyzed according to six tasks supposed to esteem their fidelity to the real operative setting by using a scoring system from zero to two. Finally, authors classified the models into five classes, from A to E, by summing the individual scores. Results: This study included 109 papers for analysis. Training models were grouped into synthetic tubes, ex vivo models (animal vessels, fresh human cadavers, human placentas) and in vivo simulators (live animals—rats, rabbits, pigs). By applying the proposed classification system, live animals and placentas obtained the highest scores, falling into class A (excellent simulators). Human cadavers and animal vessels (ex vivo) were categorized in class B (good simulators), followed by synthetic tubes (class C, reasonable simulators). Conclusions: The proposed classification system helps the neurosurgeon to analyze the available training models for microvascular anastomosis critically, and to choose the most appropriate one according to the skills they need to improve

OBJECTIVE:Guidelines for the management of pediatric severe traumatic brain injury (TBI) recommend external ventricular drainage for CSF drainage as a first-tier treatment in the intracranial pressure (ICP) pathway. However, ventriculostomy in children can sometimes be challenging because of the small size of the lateral ventricles. External lumbar drainage (ELD) may be a useful alternative; therefore, the authors analyzed the outcome of a cohort of pediatric patients who underwent ELD to manage intracranial hypertension (ICH). METHODS:This study retrospectively enrolled pediatric patients with ICH following severe TBI who underwent ELD. Radiological and clinical severity scores (Marshall classification, Rotterdam score, Injury Severity Score, and Pediatric Trauma Score) were noted. ICP and cerebral perfusion pressure (CPP) curves were analyzed 12 hours before and after the procedure. Any change in medical therapy was recorded, as well as the total volume and duration of drainage. Cerebellar tonsillar position according to the McRae line was noted before and after ELD. Glasgow Outcome Scale-Extended score at follow-up was also noted. RESULTS:Thirty patients were included, with a mean age of 8 ± 4.4 years, and a median admission Glasgow Coma Scale score of 7 ± 4 (range 3-13). ELD was performed after a median delay of 1 day (range 0-7 days), mean drainage volume/day was 296 ± 129 ml, and median duration of drainage was 7 ± 5 (range 2-12) days. Forty-three percent of the patients underwent ELD as a part of the first-tier therapy. ICP decreased after ELD (mean difference 13.4 ± 6.2 mm Hg, p < 0.001), whereas CPP increased (mean difference 10.6 ± 6.4 mm Hg, p < 0.001). Fifty-three percent of the cohort did not need any further second-tier therapy after ELD. The study found 1 case of drain revision and 3 cases of cerebellar tonsil herniation. CONCLUSIONS:These preliminary data suggest ELD is a valuable option to treat ICH in severely head-injured children, limiting the use of second-tier treatments. This pilot study should lay the foundation for a multicenter prospective trial.

AimsFGFR-fused central nervous system (CNS) tumours are rare and are usually within the glioneuronal and neuronal tumours or the paediatric-type diffuse low-grade glioma spectrum. Among this spectrum, FGFR2 fusion has been documented in tumours classified by DNA-methylation profiling as polymorphous low-grade neuroepithelial tumours of the young (PLNTY), a recently described tumour type. However, FGFR2 fusions have also been reported in glioneuronal tumours, highlighting the overlapping diagnostic criteria and challenges.MethodsWe investigated the FGFR2 fusion landscape in a French national series of tumours sent to the RENOCLIP-LOC network. We comprehensively analysed histology, radiology and molecular data including DNA-methylation profiling for 16 FGFR2-fused glioneuronal tumours.ResultsMost tumours were located in the temporal or parietal lobe with a median age at diagnosis of 7 years [1-44]. Epilepsy was the most frequent symptom. Five patients had tumour progression or recurrence with a median progression-free survival of 22.6 months. Histological phenotypes corresponding to PLNTY, GG, MVNT or unclassified tumours were recorded. Epigenetic profiling could not properly distinguish epigenetic clusters related to the GG and PLNTY methylation classes among FGFR2-fused glioneuronal tumours. However, a neuroradiological review identified strikingly distinct neuroradiological patterns.ConclusionWhile delineating tumour types among the FGFR2-fused glioneuronal tumour spectrum, by histopathology or DNA-methylation profiling, remains challenging, neuroimaging data revealed two distinct patterns that could correlate to PLNTY and ganglioglioma. However, more series including extensive histo-radio-molecular data are needed to confirm this hypothesis.

OBJECTIVE:The outcome of endoscopic third ventriculostomy (ETV) in children who had previously received shunts and who were experiencing shunt dysfunction is still discussed in terms of efficacy (success rate from 40% to 80%) and safety (0%-32.5% of complications). Reported predictive factors of secondary ETV failure are age, early onset of hydrocephalus, and prematurity. The best surgical strategy in the different subgroups of patients with shunt dysfunction is still debated. Therefore, the authors aimed to identify subgroups of patients in whom shunt treatment was associated with favorable outcome of ETV, to define the role of ETV in patients with global rostral midbrain dysfunction syndrome. METHODS:This study was a monocentric retrospective case series and a meta-analysis of children who had previously received shunts and who underwent secondary ETV for shunt dysfunction between 2012 and 2022. Clinical and MRI features were examined, along with surgical outcome, etiology of hydrocephalus, and preoperative ETV Success Score. Univariate and multivariate analyses were performed to find predictors of outcome of secondary ETV. Youden's J index was calculated on age distribution to find an optimal age cutoff. Systematic review of the literature and a meta-analysis were performed according to the PRISMA statement. RESULTS:Seventy consecutive patients were included. The overall success rate of secondary ETV was 63%. Primary obstructive hydrocephalus, age ≥ 36 months, and the presence of aqueductal obstruction were predictors of ETV success. Multivariate analysis found that age < 36 months, primary inflammatory hydrocephalus, and presence of fourth ventricular obstruction were associated with ETV failure. All patients with global rostral midbrain dysfunction syndrome experienced clinical and radiological improvement after ETV. The meta-analysis showed that postinflammatory etiology and age < 36 months were predictors of ETV failure. CONCLUSIONS:ETV is safe and effective for children with obstructive hydrocephalus experiencing shunt dysfunction, notably in cases of primary obstructive hydrocephalus with aqueductal stenosis, and among children whose age was ≥ 36 months who had postinflammatory hydrocephalus.

BACKGROUND AND OBJECTIVES: When seizure onset affects a whole hemisphere, hemispheric disconnections are efficient and safe procedures. However, both lateral peri-insular hemispherotomy and vertical paramedian hemispherotomy approaches report a failure rate around 20%, which can be explained by residual connections giving rise to persistent seizures. In this study, we present the interhemispheric vertical hemispherotomy (IVH), a technical variation of the vertical paramedian hemispherotomy approach, that aims to increase seizure control avoiding residual connections while exposing the corpus callosum. METHODS: This is a retrospective study of IVH in two centers, with analysis of clinical and MRI data and outcomes. A detailed description of the technique is provided with a video. RESULTS: IVH was performed in 39 children. The mean age at surgery was 7.2 years, and etiologies were as follows: malformations of cortical development (n = 14), Rasmussen's encephalitis (n = 10), stroke (n = 10), post-traumatic (3), and Sturge-Weber Syndrome (2). Hemispheric disconnection was complete on postoperative MRI in 34 cases. There was no mortality, hydrocephalus occurred in one case, and subdural collection occurred in four cases. A second surgery was performed in four cases because of seizure relapse (n = 3) and/or incomplete disconnection on MRI (n = 4). With a mean follow-up of 3.2 years, International League Against Epilepsy class I epilepsy outcome was obtained for 37/39 patients. CONCLUSION: IVH is a safe and effective variation of the vertical approaches for hemispheric disconnection. It allows a good exposure and anatomic control of the corpus callosum, which is a frequent site of incomplete disconnection. IVH may be limited by the thalamic volume and the ventricular size, notably in hemimegalencephaly cases.

Zolpidem is a sedative drug that has been shown to induce a paradoxical effect, restoring brain function in wide range of neurological disorders. The underlying functional mechanism of the effect of zolpidem in the brain in clinical improvement is still poorly understood. Thus, we aimed to investigate rest brain function to study zolpidem-induced symptom improvement in a patient who developed postoperative pediatric cerebellar mutism syndrome, a postoperative complication characterized by delayed onset transient mutism/reduced speech that can occur after medulloblastoma resection. The patient experienced clinical recovery after a single dose of zolpidem. Brain function was investigated using arterial spin labeling MRI and resting-state functional MRI. Imaging was performed at three time-points: preoperative, postoperative during symptoms, and after zolpidem intake when the symptoms regressed. Whole brain rest cerebral blood flow (CBF) and resting state functional connectivity using Pearson coefficient correlations between pairs of regions of interest were investigated two-by-two at the different time points. A comparison between postoperative and preoperative images showed a significant decrease in rest CBF in the left supplementary motor area, Broca’s area, and the left striatum and a decrease in functional connectivity within the dentato-thalamo-cortical and cortico-striato-pallido-thalamo-cortical loops. Post-zolpidem images showed increased CBF in the left striatum and increased functional connectivity within the disrupted loops relative to postoperative images. Thus, we observed functional changes within the broader speech network and thalamo-subcortical interactions associated with the paradoxical effect of zolpidem in promoting clinical recovery. This should encourage further functional investigations in the brain to better understand the mechanism of zolpidem in neurological recovery.

OBJECTIVE Epidural hematoma (EDH) has rarely been studied specifically in infants. The objective of this study was to investigate the outcomes of patients aged < 18 months (infants) with EDH. METHODS The authors conducted a single-center retrospective study of 48 infants aged less than 18 months who underwent an operation for a supratentorial EDH in the last decade. Clinical, radiological, and biological variables were used in a statistical analysis to identify factors predictive of radiological and clinical outcome. RESULTS Forty-seven patients were included in the final analysis. Seventeen children (36%) had cerebral ischemia on postoperative imaging, either due to stroke (cerebral herniation) or by local compression. Factors associated with ischemia after multivariate logistic regression were the presence of an initial neurological deficit (76% vs 27%, p = 0.03), low platelet count (mean 192 vs 267 per mm3, p = 0.01), low fibrinogen level (mean 1.4 vs 2.2 g/L, p = 0.04) and long intubation time (mean 65.7 vs 10.1 hours, p = 0.03). Cerebral ischemia on MRI was predictive of a poor clinical outcome. CONCLUSIONS Infants with EDH have a low mortality rate but a high risk of cerebral ischemia, along with long-term neurological sequelae.

BACKGROUND: Hydrocephalus frequently occurs with midline posterior fossa cystic collections. The classification of this heterogeneous group of developmental anomalies, including Dandy–Walker malformation, persisting Blake's pouch, retrocerebellar arachnoid cysts, and mega cisterna magna, is subject of debate. The absence of diagnostic criteria is confusing regarding the ideal management of PFCC-related hydrocephalus. OBJECTIVE: To decipher the surgical strategy for the treatment of children with PFCC-related hydrocephalus through a retrospective analysis of the surgical outcome driven by their clinical and radiological presentation. METHODS: This study enrolled patients operated of symptomatic PFCC-related hydrocephalus. Clinical and MRI features were examined, as well as the surgical outcome. Unbiased subgroup classification of the patients was performed with multiple component analysis as a function of imaging characteristics and hierarchical clustering on principal component. Outcome was assessed with binomial logistic regression and Kaplan–Meier analysis. RESULTS: Fifty-four patients were included between 2007 and 2021. Multiple component analysis suggested that cerebellar and vermian hypoplasia, vermian rotation, basal–tentorial angle, and fastigial angle were strongly correlated. Hierarchical clustering and the distribution of the patients in the bidimensional plot showed the clear segregation of 3 major clusters, which correlated with the radiological diagnosis (P < .01). Binomial logistic regression and survival analysis showed that endoscopic third ventriculostomy was an effective treatment for patients with persisting Blake's pouch, while failing to control hydrocephalus in most of patients with Dandy–Walker malformation. CONCLUSION: Preoperative MRI in patients with PFCC-related hydrocephalus is essential to better define the diagnosis. The choice of treatment strategy notably relies on correct radiological diagnosis.

Objective: This study aimed to assess the relevance of using multi-positional MRI (mMRI) to identify cranio-vertebral junction (CVJ) instability in pediatric patients with CVJ anomalies while determining objective mMRI criteria to detect this condition. Material and Methods: Data from children with CVJ anomalies who underwent a mMRI between 2017 and 2021 were retrospectively reviewed. Mobility assessment using mMRI involved: (1) morphometric analysis using hierarchical clustering on principal component analysis (HCPCA) to identify clusters of patients by considering their mobility similarities, assessed through delta (Δ) values of occipito-cervical parameters measured on mMRI; and (2) morphological analysis based on dynamic geometric CVJ models and analysis of displacement vectors between flexion and extension. Receiver operating characteristics (ROC) curves were generated for occipito-cervical parameters to establish instability cut-off values. (3) Additionally, an anatomical qualitative analysis of the CVJ was performed to identify morphological criteria of instability. Results: Forty-seven patients with CVJ anomalies were included (26 females, 21 males; mean age: 10.2 years [3–18]). HCPCA identified 2 clusters: cluster №1 (stable patients, n = 39) and cluster №2 (unstable patients, n = 8). ΔpB-C2 (pB-C2 line delta) at ≥2.5 mm (AUC 0.98) and ΔBAI (Basion-axis Interval delta) ≥ 3 mm (AUC 0.97) predicted instability with 88% sensibility and 95% specificity and 88% sensitivity and 85% specificity, respectively. Geometric CVJ shape analysis differentiated patients along a continuum, from a low to a high CVJ motion that was characterized by a subluxation of C1 in the anterior direction. Qualitative analysis found correlations between instability and C2 anomalies, including fusions with C3 (body p = 0.032; posterior arch p = 0.045; inferior articular facets p = 0.012; lateral mass p = 0.029). Conclusions: We identified a cluster of pediatric patients with CVJ instability among a cohort of CVJ anomalies that were characterized by morphometric parameters with corresponding cut-off values that could serve as objective mMRI criteria. These findings warrant further validation through prospective case–control studies.